Thermal sound recording system



June 15, 1931.

E. H. HANSEN THERMAL SOUND RECORDING SYSTEM Filed Feb. 16', 1928' 2 Sheets-Sheet 1 AMPLIFILR 14+ BATTERIES HEATING IN V EN TOR. I

June 16, 193 E. H. HANSEN 1,810,705

THERMAL SOUND RECORDING SYSTEM Filed Feb. 16, 1928 2 Sheets-Sheet 2 INVENTOR. v

Patented June 16, 1931 UNITED STATES EDMUND H. HAN SEN, OF NEW'YOBK, N. Y.

THERMAL SOUND RECORDING SYSTEM Application filed february 16, 1928. Serial No. 254,742.

This invention has reference to the recording and making of sound records with a minimum of equipment such as heretofore been found necessary. While the processes found incorporated herein are equally aplicable to the production of sound records or commercial purposes, they also permit any audible sound to be recorded under home conditions with equipment largely to be found therein.

Heretofore in the art of recording sound it is first necessary to make a inaster record of plastic wax from which a matrix is made and from this copies in the form of a more stable resinous compound are obtained. The

complicity of operations involved have precluded its adoption for simplified recording, and the use of metal discs has provided the only method capable of operation by the lay man.

The various methods wherein metal discs are employed show objectionable qualities such as shallow cutting which permits the reproducing needle to jump, and if pregrooved a great inertia to the lateral movemerit of the cutting stylus produces a record lacking in volume. Moreover the inability to reproduc'e from metallic records with steel needles of the usual type without shortening the life of the record is recognized, and the use of fibre and soft needles is also unsatisfactory due to the ability of a metal record to destroy the point of the reproducing stylus.

The present invention overcomes the diiliculties of the known art by means of a heated cutting stylus, a blank record that becomes plastic at temperatures in excess of one hundred and twenty degrees F and provides a spiral movement to the recording stylus by a. guide stylus and a pregrooving which 1s erased by means of a heated metal eraser.

The many objects of this present invention will be apparent from consideration of the specification and the drawings forming a part of this application, and throughout which like parts are designated by like characters.

The drawings herewith diagrammatically 50 illustrate certain embodiments of the invention and ways of carrying out the method and process, but the invention may be embodied in and carried out by other devices, so that Figure 2 is a diagrammatic view showingin a schematic manner the relationship of record, recording unit and supporting arm, the turntable, and attendant amplifier, batteries and sound source.

Figure 3 is a diagrammatic detail illustration of the recording mechanism and its relationship in a schematic manner to the amplifier and sound source.

Figure 4 is a detail view of the guide stylus support, the cutting and erasing stylus and their attendant heating structure.

Figure 5 is a sectional view of the compo sition record showing pregrooved structure, a portion of the record with pregrooving smoothed out and the final recording groove all with their attendant stylus in operating positions.

Referring now to the drawings and more especially Figure 1, a casing l encloses a constant speed rotating mechanism 2 to the central shaft of which is attached a turntable 3 capable of supporting the composition record at, a supporting pillar 5 acts asa pivot for the arm and recording head 6. This-mechanism previously described is similar to the standard type of disc reproducing phonograph. The special recording head 6 being attached instead of the reproducer.

Figure 2.illustrates from an elevated point the composition record it held by a centrally punched hole over the shaft and resting on the turntable attached thereto, the recording head 6 and supporting arm pivoted to the free rotating column 5, a source of sound 10, microphone ll and battery 12 which furnishes audio frequency currents that are further amplified by the audio frequency amplifier 1;) and connected to the recording head by means of the cable 15. This cable also carries the energizing current from the source 14 to the heating units incorporated.

in the recording head.

The source of sound may be one of several types, the output of a radio receiver may be connected to the amplifier as well as that ofa microphone, the input may also be that from a telephonic circuit, and it is not desired to limit the's'ource or method of generation of the recorded audio frequency currents.

Referring now to Figure 3 the recording head casing 6 supports the permanent field 17, the tips of thepole pieces encasing the windings 18 which are of a matched: impedance to the output of audio frequency amplifier 13, an armature pivotally mounted between the windings 18 the extension of which becomes the recording stylus 9, the casing 6 also carries the heated erasing stylus 8, the heater supports 23 which are heat insulating in character and around which are wound the heater wires20, the uide stylus holder and clamp screw 22 and t e guiding stylus 7.

A sub casing 21 is provided for the heater and cutting and erasing stylus protection.

It will be observed that any sound affecting the microphone 11, which for descriptive purposes may be said to be oftheva'rying resistance type, causes by means of its varying resistance characteristic a greater flow of current in the circuit proportionate to sound pressure which varies in frequency as the sound varies, thus setting up in the input circuit of the audio amplifier 18 electric currents which are am lified by means of triodes, and the output 0 this amplifier 13 is then conducted to the winding 18 through the center of which thereed armature 19 extends to a point opposite the upper pole ieces and/in a central balanced position. urrents flowing in windings 18 provide a counter magnetic field and cause a lateral displacement of the armature reed 19, and an equal displacement of the heated cutting stylus 9. Heat is supplied to the cutting stylus 9 and the erasing stylus 8 by means of the heater winding .20 which is energized by a source 14.- and the temperature sistance 16.

In Figure 4 is detailed the relationship of heater supports 23 which are of any heat resistin material, having a winding 20 thereon w ich may be standard heaterwire of sufiicient current carrying capacity to ive the maximum heat required, and protru ing through this heater coil, but not in contact therewith are the erasing stylus 8 and the recording stylus 9. A protective casing 21 restricts the heated air to the roximity of the heated styluses. In a line with the heater and erasing and cutting styluses isthe guiddetermined by the control reing stylus 7 which is clamped in the holder 22' 8 in Figure 5 is represented a cross section of a record 4 the pregrooving 24 serving as a guidechannel to the guide stylus 7 as the spiral pregrooving is rotated about the center axis, the guiding stylus 7 through its support socket and clamp 22 moves the casing 6 which in turn carries the erasing stylus 8 which having been brought to predetermined temperature by the heater system reduces the pregrooving to a flat surface 25 so that the re cording cutting stylus 9 which is of an equivalent temperature to the erasing stylus 8 is afforded free lateral movement in the heat plastic record-4 and leaves a spiral groove structure 26.

The composition of this heat plastic record may be of any material or combination of materials which can be affected by heated styluses. Hard waxes, resin, resinous compounds, certain clay and shellac compositions have all been successfully utilized and can be cut with a minimun of power on the recording stylus.

A record made according to the above process can be immediately employed for reproduction due to the fact that the area of plasticity is exceedin 1y small and extends but a few millimeters urther than the heated styluses themselves.

It is of course apparent that in addition to the method herein described and employing a pregrooved record that it is possible to employ a screw feed for imparting a lateral movement to the supporting arm and head 6 thereby dispensin with the pregrooved record, the guide sty us and the erasing sty lus, this modific -tion not a 'ecting the process of recording on a heat plastic material with a heated recording stylus.

Having described my invention, what I claim is:

1. In combination a spirally grooved heat plastic disc, an electromagnetic recording motor having a heated recording stylus, a cold guiding stylus mounted on the recording motor adapted to engage the spirally grooved disc, and a heated erasing stylus, also mounted on' said motor between the cold guiding stylus and the heated recording stylus whereby the grooving in the heat plastic disc is erased in the area preceding the recording stylus.

2. In combination a spirally pregrooved heat plastic disc, an electromagnetic recording motor and heated recordin stylus, a guiding stylus mounted on t e recording motor adapted to engage the spirally pregrooved disc and an erasing stylus also mounted on said recording motor between the guiding stylus and the heated recording stylus whereby the grooving in the heat plastic disc is erased in the area preceding the recording stylus.

3. For use in making sound records on a heat plastic pre'grooved disc, an electromagnetic recording device adapted to engage the grooves in said disc and guide said device over the surface of said disc; a heated stylus mounted on said device adapted to erase said grooves and form a smooth surface on said disc; and a second heated stylus mounted on said device adapted to form sound grooves in the smooth surface formed by said first mentioned stylus.

4. The method of sound recording upon a heat plastic pregrooved disc consistmg in: utilizing the" ooves on said disc to gulde a sound recording device thereover; erasing said grooves by a heated stylus to form a smooth surface on said disc, vand forming sound grooves in said smooth surface by a sound actuated heated stylus.

5: The method of making sound records consisting in; supplying a heat plastic pregrooved disc; guiding a sound recording device over said disc by means of said grooves; erasing said grooves by a heated stylus, and forming new sound grooves on said disc by a sound actuated heated stylus.

HANSEN. 

